In the manufacture of heat exchangers and other fluid transfer devices, it is often desirable to effect a pressure-tight seal between surfaces with unmatched contours using an adhesive or potting material to fill the gap between the surfaces. For example, when a corrugated sheet is used for heat transfer, potting material is sometimes used to fill the crevices between the sheet and a surrounding housing. Similarly, potting material is often used to fill the interstices between tubes or hollow fibers and a surrounding housing where the tubes leave the housing. Leaks are a common problem with such seals, one reason being that it is often difficult to introduce the potting material into the gaps between surfaces without entrapping air bubbles. Conventionally, the potting material is injected at exposed ends of the devices, but air bubbles rising through the potting are a problem with this procedure. A further problem with effecting such seals is ensuring the integrity of the adhesive bond between the potting and the surfaces, especially where the same potting must act as a seal between two different materials.